1. Field of the Invention
The present invention relates to a color image processing apparatus and, more particularly, to a color image processing apparatus having a function to judge a specific original.
2. Related Background Art
In recent years, as the diffusion and realization of high picture quality color original copying apparatus progress, a fear that forgery crime of bank notes, stocks and bonds, or the like is rising. To prevent such forgery, there has been proposed a method in U.S. patent application Ser. No. 478,280 whereby a pattern of a special shape is extracted from an output of a line sensor reading an original and is compared with predetermined template data, and the presence or absence of a bank note or the like is detected and, in the case where the presence of a bank note is detected, the copying operation is interrupted.
Techniques to prevent such forgery of bank notes or the like have been proposed in U.S. patent applications Ser. Nos. 351,165 and 426,044.
However, generally, a position, an angle, and the like of an original put on an original base plate of a copying apparatus are not known at all and the original to be detected mixedly exists together with other originals, so that it is extremely difficult to extract a pattern of a desired specific shape from those originals.
Even if the extraction of the desired pattern has succeeded, the pattern as an object to be extracted differs depending on the kind (e.g., denomination and issuing, country, of the bank note. The pattern matching process needs to be performed in consideration of each possible kind. Thus, the amount of data to be processed and a processing time are extremely large and long.
Further, the data amount of a template for the pattern matching increases as the number of patterns to be extracted increases. The necessary memory capacity is also very large.
On the other hand, in such apparatus, generally, a process to convert a color component of a color original into a predetermined value is effective means for discriminating a color tone of the original. For instance, when considering the case where a check is made to see if a special color tone is included in the original or not, and if it is included, the copying operation is stopped, a construction as shown in FIG. 24 is considered.
The color separated R, G, and B signals are A/D converted by an A/D converter 1301 and are subsequently shading-corrected by a shading correction circuit 1302. Output signals of the shading correction circuit 1302 are sent to a logarithm (log) converter 1303 and a lookup table (hereinafter, referred to as an LUT) 1306. Output signals from the log converter 1303 are transmitted through a masking circuit 1304 and an undercolor removal circuit (hereinafter, referred to as a UCR circuit) 1305, so that they are converted into Y, M, C, and K signals for printing and output, and a copy image is formed by those signals.
On the other hand, data of 0 or 1 indicating whether the input R, G, and B signals correspond to the color of the specific original or not has previously been written in the LUT 1306. When they correspond to the original color, the "1" signal is generated. Reference numeral 1307 denotes a counter to count the number of times this signal has the value "1" and 1308 indicates a comparator for comparing that count value with a predetermined threshold value and for outputting a "1" signal when the count value is larger than the threshold value. When the "1" signal is generated from the comparator, a selector 1309 stops the generation of the image signal and replaces it with a fixed value such as 255, thereby interrupting the formation of a copy image.
In the above construction, when it is assumed that each of the input R, G, and B signals consists of seven bits, the LUT 1306 needs a capacity of 2 Mbits. If the lookup table of such a large capacity is made operative on a pixel unit basis of an original image, however, a response time of tens of nanoseconds is required. There is a drawback that it is impossible to cope with such a response time by means of a cheap EPROM or the like.